Devices and methods for visualizing the interior of pipes or other cavities using imaging are well known in the art. For example, existing pipe inspection systems may include a camera head coupled to a video push-cable, with the camera head pushed into the pipe to facilitate displaying, recording and/or mapping of the pipe interior by capturing images or video for display or recording.
Conventional pipe inspection systems generally include a semi-rigid video push-cable that provides a mechanical connection between a rotatable drum reel, used to dispense the video push-cable and urge an attached camera head down a pipe, as well as multiple electrical conductors and corresponding connections that provide power to and/or images, video, and/or control signals between the camera head and camera control device. The camera head may include imaging sensor (imagers), associated electronics, optics, lighting elements (e.g., LEDs) and/or other sensors to generate images or video of the pipe's interior, as well as to provide additional information. Images and video taken within the pipe may be transferred via electrical connections in the video push-cable to a CCU (or other device) connected to the drum reel at the ground surface, typically on dedicated conductors. The CCU may display and/or store the images or video, and may also control operation of the camera head. Some existing video push-cables also transmit DC electrical power from the CCU to the camera head to power camera head electronics and lights, also typically on dedicated conductors.
Existing video push-cables used for pipe inspection systems are often helically wrapped with filler rods and conductors wound around a semi-rigid central push-rod element that is non-conductive. The central push-rod element is typically a high-strength rod of composite material, such as fiberglass, which provides the stiffness necessary to deploy the video push-cable a considerable distance, yet is flexible enough to allow bending around sharp turns in pipes or other voids. These video push-cables, however, can be difficult to deploy or retract, and/or may cause problems with signaling and power provision when used with newer camera heads. Further, existing push cables typically have two or more conductors positioned around or outside the central push-rod element. These conductors are difficult to terminate in the field (such as when a push-cable breaks during deployment or retraction). Normally a broken push-cable requires a return to a repair facility, where conductors must be soldered back onto termination connectors or splice connectors to get the push-cable back into service.
As noted above, coaxial cables are well known in the art. However, coaxial cables known in the art are designed to minimize capacitive loss, and teach towards utilizing materials with low dielectric constants as an insulator positioned between inner and outer/shield conductors. Such low dielectric constant materials are used to achieve a target impedance with a minimal cross-sectional diameter. Commonly used dielectric materials may further be chosen so as to reduce power loss by selecting an appropriate loss tangent, as well as for providing a suitable modulus of elasticity to allow the cable to easily bend and flex. As such, coaxial cables known in the art lack in the elastic modulus, stiffness, and strength required of a push-cable.
Accordingly, there is a need in the art to address the above-described as well as other problems to provide enhanced performance video push-cables.